1. Field of the Invention
This invention relates to an interleaved circuit of a flexure used in a disk drive for an information processing apparatus, such as a personal computer.
2. Description of the Related Art
A hard disk drive (HDD) is used in an information processing apparatus, such as a personal computer. The HDD comprises a magnetic disk rotatable about a spindle, a carriage turnable about a pivot, etc. A disk drive suspension is disposed on an arm of the carriage.
The disk drive suspension comprises a baseplate, load beam, etc. A flexure is disposed on the load beam. A slider is mounted on a gimbal portion formed near the distal end of the flexure. The slider is provided with elements (transducers) for accessing data, that is, for reading or writing data. The suspension, flexure, etc., constitute a head gimbal assembly.
Flexures are practically available in various forms depending on required specifications. A flexure with conductors is a known example. A circuit of the flexure of this type comprises a metal base, insulating layer formed on the metal base, a plurality of conductors formed on the insulating layer, etc. The metal base is formed of a thin plate of stainless steel. The insulating layer consists mainly of an electrically insulating material, such as polyimide. Each conductor is a copper member, one end of which is connected to an element (e.g., magnetoresistive element) of a slider. The other end of the conductor is connected to an amplifier or the like of a disk drive.
The circuit of the flexure is expected to be reduced in impedance, in order to match the amplifier with the element of the slider and reduce energy consumption. A reduction in inductance is also required. To achieve high-speed data transfer, moreover, such characteristics (low-attenuation broadband characteristics) are required that the attenuation is low even in a high-frequency range.
These requirements can be effectively satisfied by a flexure with conductors that comprises multi-trace transmission lines. A circuit with multi-trace transmission lines is also called an interleaved circuit. Examples of flexures with conductors comprising an interleaved circuit are disclosed in U.S. Pat. No. 5,717,547 (Patent Document 1) and Jpn. Pat. Appln. KOKAI Publication No. 2010-267334 (Patent Document 2).
A conventional interleaved circuit comprises a metal base, insulating layer formed on the metal base, a plurality of (e.g., two) branch conductors branching from a first conductor, and a plurality of (e.g., two) branch conductors branching from a second conductor. These branch conductors are formed on the insulating layer and covered by a cover resin layer. A flexure with conductors comprising such an interleaved circuit is said to be low in attenuation in a high-frequency band and suitable for high-speed data transfer.
In the interleaved circuit described above, the frequency band can be enhanced by forming an opening in a part (that part on which the branch conductors are arranged) of the metal base. However, the interleaved circuit in which the opening is simply formed in the metal base can only limitedly achieve low-loss broadband characteristics.